Solenoid valve

ABSTRACT

A solenoid valve includes a coil assembly accommodated in a solenoid housing having an end wall at one end thereof. A stationary core is magnetically coupled to the end wall and inserted into one end of a center bore, and a movable core opposed to the stationary core is inserted into the other end of the center bore. A yoke plate opposed to the other end of the coil assembly is coupled to the other end of the solenoid housing, and a collar made of a non-magnetic material adapted to guide the axial movement of the movable core is inserted into the other end of the center bore through a central portion of the yoke plate. A rod operatively connected to the movable core is connected to a valve member accommodated in a valve housing connected to the solenoid housing. In such solenoid valve, in order to facilitate the processing and assembling of the collar, the movable core and the rod and to provide a reduction in cost, the valve housing is provided with a guide for guiding the axial movement of the rod, and one end of the rod is put into coaxial abutment against the other end of the movable core.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solenoid valve, and particularly toan improvement in a solenoid valve including a coil assemblyaccommodated in a solenoid housing made of a magnetic metal and havingan end wall at one end thereof, a movable core which is opposed to astationary core magnetically connected to the end wall and inserted intoone end of a center bore and which is inserted into the other end of thecenter bore, a yoke plate made of a magnetic metal which is opposed tothe other end of the coil assembly and coupled to the other end of thesolenoid housing, a collar made of a non-magnetic material which isadapted to guide the axial movement of the movable core and insertedinto the other end of the center bore through the central portion of theyoke plate, a valve member accommodated in a valve housing connected tothe solenoid housing, and a rod operatively connected to the movablecore and connected to the valve member.

2. Description of the Related Art

Such a solenoid valve is conventionally well-known, for example, fromJapanese Patent Application Laid-open No.3-157576 and the like. In thissolenoid valve, one end of the rod is coaxially fitted in the movablecore.

However, the conventionally known solenoid valve is of an arrangementsuch that the movable core and the rod are substantially integral witheach other, and moreover the axial movement of only the movable core isguided. For this reason, the position of an axial center of the rod isinfluenced by the concentricity between the movable core and the rod andthe accuracy of the position of the axial center of the collar adaptedto guide the movable core. To ensure the smooth axial movements of themovable core and the rod within the collar and the valve housing, theprocessing accuracy and assembling accuracy of the collar adapted toguide the movable core, the movable core and the rod must be increased,thereby bringing about an increase in cost.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide asolenoid valve, wherein the processing and assembling of the collar, themovable core and the rod can be facilitated to provide a reduction incost.

To achieve the above object, according to a first aspect and feature ofthe present invention, there is provided a solenoid valve comprising acoil assembly including a bobbin made of a synthetic resin and having acenter bore, and a coil wound around the bobbin, the coil assembly beingaccommodated in a solenoid housing made of a magnetic metal and havingan end wall at one end thereof; a stationary core magnetically coupledto the end wall and inserted into one end of the center bore; a movablecore opposed to the stationary core and inserted into the other end ofthe center bore; a yoke plate made of a magnetic metal, which has athrough-bore in its central portion and which is opposed to the otherend of the coil assembly and coupled to the other end of the solenoidhousing; a collar made of a non-magnetic material adapted to guide theaxial movement of the movable core and inserted into the other end ofthe center bore through the through-bore; and a valve member which isaccommodated in a valve housing connected to the yoke plate and to whicha rod operatively connected to the movable core is connected, whereinthe valve housing is provided with a guide portion for guiding the axialmovement of the rod, and one end of the rod is put into coaxial abutmentagainst the other end of the movable core.

With such arrangement of the first feature, the movable core and the rodare separate from each other and hence, it is unnecessary to increasethe processing accuracy for assembling the movable core and the rod toeach other, and even if the axial centers of the movable core and therod are offset slightly from each other, an adverse influence cannot beexerted to the axial movement of the movable core and the rod separatelyguided by the collar and the guide. Therefore, it is possible tofacilitate the processing and assembling of the collar, the movable coreand the rod, thereby providing a reduction in cost.

According to a second aspect and feature of the present invention, inaddition to the arrangement of the first feature, the valve housing madeof a synthetic resin is integrally connected to the bobbin through aplurality of connecting bores provided in the yoke plate. With sucharrangement, the bobbin, the yoke plate and the valve housing areintegrally connected to one another and hence, the accuracy of the axialcenters of the bobbin, the yoke plate and the valve housing can beenhanced easily.

According to a third aspect and feature of the present invention, inaddition to the arrangement of the second feature, an outer periphery ofthe yoke plate integrally coupled by molding between the valve housingand the bobbin is coupled to the solenoid housing on the side oppositefrom the end wall. With such arrangement, the assembling can befacilitated by integrally coupling the yoke plate upon the formation ofthe bobbin and the valve housing connected to each other through theconnecting bores in the yoke plate.

According to a fourth aspect and feature of the present invention, inaddition to the arrangement of the first feature, the collar which hasat one end thereof an outward-facing collar portion protruding radiallyoutwards and opposed to an inner surface of the center bore ispress-fitted into the through-bore. With such arrangement, the collar ispress-fitted into the through-bore using the outward-facing collarportion exerting no influence to the sliding movement of the movablecore within the collar. Thus, it is possible to press-fit the collarhaving a thickness at a small valve to the utmost into the through-bore,whereby the distance between the movable core and the yoke plate can beset at a small value to the utmost to enhance the magneticcharacteristic, and the axial movement of the movable core can be guidedby the collar fixed to the yoke plate.

According to a fifth aspect and feature of the present invention, inaddition to the arrangement of the fourth feature, the collar isprovided at the other end thereof with an inward-facing collar portionprotruding radially outwards, and one end of the rod through which theinward-facing collar portion is axially movably passed is put intocoaxial abutment against the other end of the movable core within thecollar. With such arrangement, the other end of the collar issubstantially occluded by the rod and hence, it is possible to preventthe entrance of dust into the collar to the utmost.

According to a sixth aspect and feature of the present invention, inaddition to the arrangement of the first feature, the yoke plate has acylindrical portion integrally provided at a center thereof to protrudeon the side opposite from the coil assembly and to define a portion ofthe through-bore. With such arrangement, the collar is supported over anaxially relatively long distance by the cylindrical portion integralwith the yoke plate and in this manner, the axis of the collar can beprevented to the utmost from being inclined. In addition, it is possibleto increase the area of a portion of the yoke plate opposed to an outersurface of the movable core through the collar, and to provide anenhancement in magnetic characteristic by an increase in area of amagnetic path.

According to a seventh aspect and feature of the present invention, inaddition to the arrangement of the first or sixth feature, the movablecore is integrally provided with a smaller-diameter portion insertedinto the collar, and a larger-diameter portion formed to have a diameterlarger than that of the smaller-diameter portion and coaxially connectedto one end of the smaller-diameter portion at a location outside axiallyone end of the collar in such a manner that it is opposed to the otherend of the stationary core. With such arrangement, despite the insertionof the collar into the center bore in the bobbin, the area of oppositionof the movable and stationary cores to each other can be set at arelatively large value, and the magnetic characteristic can be enhanced.Moreover, by cooperation with the increase in area of the magnetic pathaccording to the arrangement of the sixth feature, the magneticcharacteristic can be further enhanced.

According to an eighth aspect and feature of the present invention, inaddition to the arrangement of the seventh feature, the movable core hasa recess coaxially provided at one end thereof, so that a portion of areturn spring mounted between the movable and stationary cores isaccommodated in the recess. With such arrangement, despite the provisionof the larger-diameter portion at one end of the movable core, themovable core can be lightened in weight, and the rapid axial movement ofthe movable core is possible.

According to a ninth aspect and feature of the present invention, inaddition to the arrangement of the seventh feature, the larger-diameterportion has a groove provided in its outer surface to extend over theaxially entire length of the larger-diameter portion to define a flowpath between the outer surface of the larger-diameter portion and theinner surface of the center bore. With such arrangement, a fluid can beallowed to flow between opposite ends of the larger-diameter portionwith the axial movement of the movable core, thereby contributing to therapid axial movement of the movable core.

According to a tenth aspect and feature of the present invention, inaddition to the arrangement of the ninth feature, the movable core has arecess coaxially provided at one end thereof, so that a portion of areturn spring mounted between the movable and stationary cores isaccommodated in the recess, and a communication bore provided at one endthereof to connect the flow path and the recess to each other. With sucharrangement, the movement of the fluid with the axial movement of themovable core can be smoothened, whereby the movable core can be movedmore quickly.

According to an eleventh aspect and feature of the present invention, inaddition to the arrangement of the first feature, the rod is formed atone end thereof with an abutment face spherical about a phantom centeron the axis of the rod, the abutment face abutting against the other endof the movable core. With such arrangement, even if a force from themovable core in a direction offset from the axis thereof is exerted tothe rod, an influence cannot be exerted to the axial movement of therod.

According to a twelfth aspect and feature of the present invention, inaddition to the arrangement of the first feature, the bobbin has anaccommodating recess provided at one end thereof to open in an opposedrelation to the end wall of the solenoid housing, and a spring made of aconductive metal and adapted to exhibit a spring force for biasing thecoil assembly toward the yoke plate is mounted between the end wall andan earth plate accommodated in the accommodating recess and leading tothe coil. With such arrangement, the earth plate can be electricallyconnected to the solenoid housing, using the spring for supporting thecoil assembly stably within the solenoid housing, whereby the solenoidhousing can be grounded. Thus, it is unnecessary to mount a terminalmember for the earth plate and hence, the number of parts can bereduced.

According to a thirteenth aspect and feature of the present invention,in addition to the arrangement of the first feature, a connecting shaftportion tightly passed through a through-bore provided in the end wallis integrally connected to the bobbin, and a coupler support plate isintegrally formed on a couple made of a synthetic resin to which aterminal member connected to the coil faces, so that the coupler supportplate abuts against the outer surface of the end wall, the couplersupport plate and the connecting shaft portion inserted through awelding bore provided in the coupler support plate being welded to eachother.

With such arrangement of the thirteenth feature, the coupler separatefrom the coil assembly can be mounted to the outer surface of the endwall of the housing and hence, despite the change in shape of thecoupler, it is unnecessary to change the portions excluding the coupler,leading to enhanced general-purpose properties. Moreover, the connectingshaft portion is tightly passed through the through-bore provided in theend wall of the housing and hence, the position of the bobbin, i.e., thecoil assembly relative to the solenoid housing within a planeperpendicular to the axis of the solenoid housing can be determinedconstant. In addition, by the fitting of the terminal member into thecoupler, the position of the coupler relative to the coil assemblywithin the plane perpendicular to the axis of the solenoid housing canbe determined constant, and thus, the coupler can be fixed firmly andstably to an outer surface of an end portion of the solenoid housinghaving a rigidity.

According to a fourteenth aspect and feature of the present invention,in addition to the arrangement of the thirteenth feature, the couplersupport plate is formed integrally with the coupler separate from thecoil assembly, and the terminal member passed through aterminal-penetration bore provided in the end wall is fitted into thecoupler. With such arrangement, the coupler separate from the coilassembly can be mounted to the outer surface of the end wall of thesolenoid housing and hence, despite the change in shape of the coupler,it is unnecessary to change the portions excluding the coupler, leadingto enhanced general-purpose properties.

According to a fifteenth aspect and feature of the present invention, inaddition to the arrangement of the thirteenth or fourteenth feature, atleast two sets of the welding bores and the connecting shaft portionsare disposed at locations where the coupler is interposed between them.With such arrangement, it is possible to reliably ensure the mountingand fixing of the coupler to the outer surface of the end wall of thesolenoid housing.

According to a sixteenth aspect and feature of the present invention, inaddition to the arrangement of the thirteenth or fourteenth feature, thecoupler support plate is formed into a disk shape. With sucharrangement, the load strength of the coupler over the entire peripheryof the solenoid housing can be increased.

According to a seventeenth aspect and feature of the present invention,in addition to the arrangement of the thirteenth or fourteenth feature,a protrusion of the connecting shaft portion from the welding bore ispushed and crushed axially and thermally welded to the coupler supportplate. With such arrangement, to weld the connecting shaft portion andthe coupler support plate to each other, expensive welding equipment andwelding jig for a ultrasonic welding and the like are not required, andinexpensive equipment and jig can be employed.

According to an eighteenth aspect and feature of the present invention,in addition to the arrangement of the seventeenth feature, the weldingbore is provided, at its end opposite from the end wall, with a taperedportion with its diameter being larger at a location farther from theend wall. With such arrangement, the weld strength in a directionperpendicular to the axial directions of the welding bore can beincreased.

According to a nineteenth aspect and feature of the present invention,in addition to the arrangement of the thirteenth feature, a base portionof the terminal member adjacent the bobbin is covered with a coveringportion made of a synthetic resin formed integrally with the bobbin andfitted into the terminal-penetration bore. With such arrangement, aguide portion can be utilized for positioning of the bobbin and thecoupler relative to the solenoid housing, while providing the insulationbetween the terminal member and the solenoid housing. Thus, incooperation with the extension of the connecting shaft portion throughthe through-bore in the solenoid housing, the positioning of the bobbinand the coupler relative to the solenoid housing can be ensured morefirmly.

According to a twentieth aspect and feature of the present invention, inaddition to the arrangement of the first feature, the valve housingincludes a guide bore coaxially communicating at one end thereof withthe through-bore; a partition wall having a first valve bore throughwhich the other end of the rod coaxially disposed in the guide bore isloosely inserted, and a first valve seat, to a central portion of whichthe first valve bore faces on the side opposite from the guide bore; anda fitting bore which is disposed coaxially with the guide bore with thepartition wall disposed between the fitting bore and the other end ofthe guide bore and which has a step facing on the side opposite from thepartition wall; and a valve seat member having a second valve seat atone end and provided at the other end with a limiting collar portionprotruding radially outwards is fitted and fixed in the fitting bore insuch a manner that a valve chest is provided between the valve seatmember and the partition wall and the limiting collar portion abutsagainst the step. With such arrangement, in a state in which the valveseat member has been fitted and fixed in the valve housing, the secondvalve seat and the step of the valve housing are disposed at axiallydisplaced locations. Thus, the determination of the position of thesecond valve seat corresponding to the diversification of the length andthe shape of the valve housing can be achieved by only changing thelength between the second valve seat and the limiting collar portion,leading to enhanced general-purpose properties.

According to a twenty-first aspect and feature of the present invention,in addition to the arrangement of the twentieth feature, the valve seatmember has a second valve bore provided therein over the axially entirelength with one end opening into a central portion of the second valveseat, and a filter is disposed to face the other end of the second valvebore with the limiting collar portion of the valve seat memberinterposed between an outer periphery of the filter and the step, theother end of the valve housing being engaged with the outer periphery ofthe filter by caulking. With such arrangement, it is possible tofacilitate the assembling of the valve seat member and the filter to thevalve housing.

According to a twenty-second aspect and feature of the presentinvention, in addition to the arrangement of the first feature, a valveseat member is fitted and fixed in the valve housing to define a valvechest between the valve seat member and the valve housing, and thespherical valve member is accommodated in the valve chest, so that itcan be seated on a valve seat provided on the valve seat member, thevalve seat member having the valve seat at one end being provided at theother end thereof with a limiting collar portion protruding radiallyoutwards, the valve housing being provided with a step adapted to abutagainst the limiting collar portion upon fitting of the valve seatmember to define an end of movement of the valve seat member in afitting direction. With such arrangement, in a state in which the valveseat member has been fitted and fixed in the valve housing, the valveseat and the step of the valve housing are disposed at axially displacedlocations. Thus, the determination of the position of the valve seatcorresponding to the diversification of the length and the shape of thevalve housing can be achieved by only changing the length between thesecond valve seat and the limiting collar portion, leading to enhancedgeneral-purpose properties.

According to a twenty-third aspect and feature of the present invention,in addition to the arrangement of the twenty-second feature, the valveseat is formed into a tapered shape. With such arrangement, theseatability of the spherical valve member on the valve seat can beenhanced, and a stable seated state of the valve member can bemaintained when the valve member is in its closed state.

According to a twenty-fourth aspect and feature of the presentinvention, in addition to the arrangement of the twenty-second feature,the valve housing is provided with a fitting bore coaxial with an axisof the movable core, and an O-ring is mounted to an outer periphery ofthe valve seat member fitted in the fitting bore with the limitingcollar portion abutting against the annular step formed on an innersurface of the fitting bore, so that the O-ring comes into repulsivecontact with the inner surface of the fitting bore. With sucharrangement, the valve seat member can be fitted into the valve housing,while maintaining the sealability between the valve chest and theoutside.

According to a twenty-fifth aspect and feature of the present invention,in addition to the arrangement of the twenty-second feature, valvemember guide members are integrally connected to one end of the valveseat member to come into contact with the valve member at a plurality ofpoints around an axis of the valve seat member to guide the movement ofthe valve member. With such arrangement, the valve member can be guidedwith a good accuracy to the valve seat.

According to a twenty-sixth aspect and feature of the present invention,in addition to the arrangement of the twenty-second feature, the valveseat member is formed of a synthetic resin. With such arrangement, it ispossible to easily produce the valve seat member, thereby providing areduction in cost.

According to a twenty-seventh aspect and feature of the presentinvention, in addition to the arrangement of the twenty-second feature,the valve seat member is formed of a metal. With such arrangement, theaccuracy of formation of the valve seat can be enhanced to improve theseatability.

According to a twenty-eighth aspect and feature of the presentinvention, in addition to the arrangement of the twenty-fourth feature,the valve seat member has a valve bore provided therein over the axiallyentire length with one end opening into a central portion of the valveseat, and a filter is disposed to face the other end of the valve borewith the limiting collar portion of the valve seat member beinginterposed between an outer periphery of the filter and the step, thevalve housing being engaged with the outer periphery of the filter bycaulking. With such arrangement, it is possible to facilitate theassembling of the valve seat member and the filter to the valve housing.

According to a twenty-ninth aspect and feature of the present invention,in addition to the arrangement of the twenty-eighth feature, the filtercomprises a net-shaped member supported on an inner periphery of a framemember formed into a ring shape, and the valve bore has a tapered boreportion coaxially provided at the other end thereof with the diameter ofits larger-diameter end being larger at a location closer to the filter,while corresponding to the inner diameter of the frame member. With sucharrangement, a fluid can be allowed to flow through the substantiallyentire net-shaped member of the filter, whereby the resistance to theflowing of the fluid can be suppressed.

The above and other objects, features and advantages of the inventionwill become apparent from the following description of the preferredembodiments taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 4 show a first embodiment of the present invention, wherein

FIG. 1 is a vertical sectional view of a three-way solenoid valve;

FIG. 2 is an enlarged sectional view taken along a line 2—2 in FIG. 1;

FIG. 3 is an exploded perspective view of a solenoid section;

FIG. 4 is an enlarged view of a lower portion of the solenoid valveshown in FIG. 2;

FIGS. 5 and 6 shown a second embodiment of the present invention,wherein

FIG. 5 is a vertical sectional view of a valve section corresponding tothe FIG. 4;

FIG. 6 is a sectional view taken along a line 6—6 in FIG. 5; and

FIG. 7 is a view similar to FIG. 6, but showing a modification to thesecond embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention will now be described withreference to FIGS. 1 to 4. Referring first to FIG. 1, a three-waysolenoid valve 14 is comprised of a valve section 15 operated to beswitched over between a state in which it permits an inlet passage 11leading to a fluid supply source (not shown) to communicate with anoutlet passage 12 leading to a fluid-pressure actuator (not shown) andcuts off the communication between a discharge passage 13 leading to areservoir (not shown) and the outlet passage 12 and a state in which itcuts off the communication between the inlet passage 11 and the outletpassage 12 and permits the discharge passage 13 and the outlet passage12 to communicate with each other, and a solenoid section 16 adapted toexhibit an electromagnetic force for switching over the valve section15.

Referring also to FIGS. 2 and 3, the solenoid section 16 includes a coilassembly 17, a solenoid housing 18 which is made of a magnetic metal andin which the coil assembly 17 is accommodated, a yoke plate 19 made of amagnetic metal and coupled to the solenoid housing 18, a stationary core20 integrally formed on the solenoid housing 18, and a movable core 21opposed to the stationary core 20.

The coil assembly 17 is comprised of a bobbin 23 made of a syntheticresin and having a central bore 22, a coil 24 wound around the bobbin23, and a covering portion 25. The covering portion 25 is formed, forexample, by winding a tape made of a synthetic resin around the coil 24wound around the bobbin 23.

The solenoid housing 18 is formed into a bottomed cylindrical shape withan end wall 18 a integrally provided at one end thereof and opposed toaxially one end of the coil assembly 17. The stationary core 20 formedinto a rod-shape and inserted from the side of one end into the centralbore 22 is connected at its one end, for example, integrally to acentral portion of the end wall 18 a of the solenoid housing 18, wherebythe stationary core 20 is magnetically coupled to the solenoid housing18.

The yoke plate 19 has a through-bore 26 corresponding to the centralbore 22 at its central portion, and is opposed to the other end of thecoil assembly 17 with its outer periphery coupled to the other end ofthe solenoid housing 18 by caulking or by another means. Moreover, theyoke plate 19 is integrally provided at its center with a cylindricalportion 19 a defining a portion of the through-bore 26 and protruding onthe side opposite from the coil assembly 17.

The axial movement of the movable core 21 is guided by a cylindricalcollar 27 made of a non-magnetic material, e.g., a stainless steel. Thecollar 27 is press-fitted into and through the through-bore 26 andinserted into the other end of the central bore 22. The collar 27 isprovided at one end thereof with an outward-facing collar portion 27 aprotruding radially outwards and opposed to an inner surface of thecentral bore 22, and at the other end thereof with an inward-facingcollar portion 27 b protruding radially inwards.

On the other hand, the movable core 21 is integrally provided with asmaller-diameter portion 21 a inserted into the collar 27, and alarger-diameter portion 21 b formed to have a diameter larger than thatof the smaller-diameter portion 21 a and opposed to the other end of thestationary core 20. The larger-diameter portion 21 b is coaxiallyconnected to one end of the smaller-diameter portion 21 a at a locationoutside the axially one end of the collar 27, and the movable core 21has a recess 29 coaxially provided at one end thereof for accommodatinga portion of a return spring 28 mounted between the movable core 21 andthe stationary core 20.

For example a plurality of grooves 31 are provided in an outer surfaceof the larger-diameter portion 21 b to extend over the axially entirelength of the larger-diameter portion 21 b to define a flow path 30between the outer surface of the larger-diameter portion 21 b and theinner surface of the central bore 22, and a communication bore 32 isprovided in the movable core 21 to connect the flow path 30 and therecess 29 to each other.

A coupler 36 made of a synthetic resin is disposed outside the solenoidhousing 18, and a terminal member 35 extended from the bobbin 23 andleading to one end of the coil 24 included in the coil assembly 17 facesthe inside of the coupler 36. The coupler 36 is formed integrally with adisk-shaped coupler support plate 37 put into abutment against an outersurface of the end wall 18 a of the solenoid housing 18.

A pair of through-bore 38, 38 and a terminal-penetration bore 39 areprovided in the end wall 18 a of the solenoid housing 18, and forexample a pair of connecting shaft portions 20, 20 extending through thethrough-bores 38, 38 are integrally connected at one ends thereof to thebobbin 23. On the other hand, a pair of welding bores 41, 41corresponding to the through-bores 38, 38 are provided in the couplersupport plate 37, and tapered portions 41 a, 41 a having the diameterlarger at a location farther from the end wall 18 are provided at endsof the welding bores 41, 41 opposite from the end wall 18 a.

The connecting shaft portions 40, 40 are inserted through the weldingbores 41, 41, respectively, and the other ends of the connecting shaftportions 40, 40 and the coupler support plate 37 are thermally welded toeach other in such a manner that portions of the connecting shaftportions 40, 40 protruding from the welding bores 41, 41 are pressed andcrushed axially.

Moreover, two sets of the welding bores 41, 41 and the connecting shaftportions 40, 40 are disposed at locations where the coupler 36 issandwiched between them.

A base portion of the terminal member 35 on the bobbin 23 side iscovered with a covering portion 42 of a synthetic resin formedintegrally with the bobbin 23 and fitted into the terminal-penetrationbore 39, and the terminal member 35 is bent into a substantially L-shapeand fitted to the coupler 36.

A ring-shaped earth plate 43 connected to the other end of the coil 23included in the coil assembly 17 is accommodated in an accommodatingrecess 44 provided in an outer surface of one end of the bobbin 23, anda spring 45 is mounted between the earth plate 43 and the end wall 18 afor urging the coil assembly 17 toward the yoke plate 19 to maintain theposition of the coil assembly 17 constant within the solenoid housing18. Moreover, the spring 45 is formed of a conductive metal, and theearth plate 43 is electrically connected to the solenoid housing 18through the spring 45. Further, a bracket 46 for supporting a supportmember made of a metal (not shown) is welded to the solenoid housing 18,and the other end of the coil 24 is grounded through the earth plate 43,the spring 45, the solenoid housing 18, the bracket 46 and the supportmember.

Referring also to FIG. 4, the valve section 15 includes a valve housing48 made of a synthetic resin, a spherical valve member 49 accommodatedin the valve housing 48, and a rod 50 which operatively connects themovable core 21 of the solenoid section 16 and the spherical valvemember 49 to each other.

The valve housing 48 is integrally connected at one end thereof to thebobbin 23 of the coil assembly 17 in the solenoid section 16. Morespecifically, a plurality of connecting bores 54 are provided in theyoke plate 19, and the valve housing 48 integrally leading to the bobbin23 through the connecting bores 54, the bobbin 23 and the yoke plate 19sandwiched between the valve housing 48 and the bobbin 23 are integrallycoupled to one another by molding.

The valve housing 48 includes a guide bore 55 coaxially communicating atone end thereof with the through-bore 26 in the yoke plate 19 includedin the solenoid section 15, a partition wall 57 having a first valvebore 61 coaxial with the guide bore 55 and a first valve seat 62, to acentral portion of which the first valve bore 61 faces at the sideopposite from the guide bore 55, and a fitting bore 56 which is disposedcoaxially with the guide bore 55 with the partition wall 57 disposedbetween the fitting bore 56 and the other end of the guide bore 55 andwhich has a step 65 formed on its inner surface at an end opposite fromthe partition wall 57 to face on the side opposite from the partitionwall 57.

The rod 50 is disposed coaxially in the guide bore 55 and is provided atthe other end with a smaller-diameter portion 50 a loosely insertedthrough the first valve bore 61. A cylindrical member made of a metaland functioning as a guide 52 for guiding the axial movement of the rod50 is press-fitted into the guide bore 55. For example a plurality ofgrooves 52 a are provided in an outer periphery of the cylindricalmember over the entire length to define a flow path 34 between thecylindrical member and the valve housing 48, and an open chamber 59 isdefined in the valve housing 48 between the yoke plate 19 of thesolenoid section 16 and the guide 52 to lead to the discharge passage13.

The inward-facing collar portion 27 b protruding radially inwards isintegrally provided at the other end 27 in the solenoid section 16, andone end of the rod 50 axially movably passed through the inward-facingcollar portion 27 b is put into coaxial abutment against the other endof the movable core 21 within the collar 27. Moreover, a sphericalabutment face 50 b having a phantom center on an axis of the rod 50 isformed at one end of the rod 50 to abut against the other end of themovable core 21.

A valve seat member 53 having a second tapered valve seat 64 at one endthereof and a limiting collar portion 53 a protruding radially outwardsat the other end is fitted into the fitting bore 56 in such a mannerthan a valve chest 58 is defined between the valve seat member 53 andthe partition wall 57 to communicate with the outlet passage 12, and thelimiting collar portion 53 a abuts against the step 64. An O-ring 66 ismounted to an outer periphery of the valve seat member 53 to come intorepulsive contact with the inner surface of the fitting bore 56.

The spherical valve member 49 capable of being seated alternatively onthe first and second valve seats 62 and 64 is accommodated in the valvechest 58, and the smaller-diameter portion 50 a of the rod 50 looselypassed through the first valve bore 61 abuts against the spherical valvemember 49.

A second valve bore 63 is provided in the valve seat member 53 over theaxially entire length, and opens at one end thereof into the centralportion of the second valve seat 64, and a filter 67 is disposed betweenthe second valve bore 63 and the inlet passage 11 to face the other endof second valve bore 63 with a limiting collar portion 53 a of the valveseat member 53 interposed between an outer periphery of the filter 67and the step 65, and the other end of the valve housing 48 is engaged bycaulking such as thermal caulking with the outer periphery of the filter67. Thus, the valve seat member 53 fitted in the fitting bore 56 isfixed to the valve housing 48.

The filter 67 comprises a net-shaped member 69 supported on an innerperiphery of a frame member 68 formed into a ring shape, and the secondvalve bore 63 has a tapered bore portion 63 a coaxially provided at theother end thereof, with the diameter of a larger-diameter end of thetapered bore portion 63 a being larger at a location closer to thefilter 67, while corresponding to the inner diameter of the frame member68.

The valve seat member 53 may be formed of a metal or a synthetic resin.When the valve seat member 53 is formed of a metal, the forming accuracyof the second valve seat 64 can be enhanced, leading to an improvedseatability. When the valve seat member 53 is formed of a syntheticresin, the fabrication of the valve seat member 53 can be facilitated,leading to a reduction in cost.

The operation of the first embodiment will be described below. Whenelectric current is supplied to the coil 24 of the solenoid section 16,the movable core 21 is attracted toward the stationary core 20 against aspring force of the return spring 28 and hence, in a state in which afluid pressure has been applied from the inlet passage 11 through thefilter 67 to the second valve bore 63, the spherical valve member 49 ispushed upwards away from the second valve seat 64 and seated on thefirst valve seat 62. Therefore, the second valve bore 63 is opened, andthe first valve bore 61 is closed, thereby causing the inlet passage 11to communicate with the outlet passage 12, and causing the outletpassage 12 and the discharge passage 13 to be put out of communicationwith each other.

On the other hand, when the supplying of electric current to the coil 24of the coil section 16 is stopped, the movable core 21 is operated in adirection away from the stationary core 20 under the action of thespring force of the return spring 28, and hence, the spherical valvemember 49 is urged by the rod 50, so that it is unseated from the firstvalve seat 62 and seated on the second valve seat 64. Therefore, thefirst valve 61 is opened, and the second valve bore 63 is closed,thereby causing the outlet passage 12 to communicate with the dischargepassage 13, and causing the outlet passage 12 and the inlet passage 11to be put out of communication with each other.

In the solenoid section 16 in such three-way solenoid valve 14, one endof each of the connecting shaft portions 40, 40 of the synthetic resinextending through the through-bores 38, 38 provided in the end wall 18 aof the solenoid housing 18 is connected to the bobbin 23; the couplersupport plate 37 formed integrally with the coupler 36 separate from thecoil assembly 17 is welded to the other ends of the connecting shaftportions 40, 40 inserted through the welding bores 41, 41 in the couplersupport plate 37, and the terminal member 35 extending through theterminal-penetration bore 39 in the end wall 18 a is fitted in thecoupler 36. Therefore, the coupler 36 separate from the coil assembly 17can be mounted to the outer surface of the end wall 18 a of the solenoidhousing 18, and despite the change in shape of the coupler 36, it isunnecessary to change the portions excluding the coupler 36, therebyenhancing the general-purpose properties. Moreover, the connecting shaftportions 40, 40 and the bobbin 23 are formed integrally with each otherand hence, it is possible to avoid an increase in number of parts and anincrease in number of assembling steps due to the provision of theconnecting shaft portions 40, 40.

When the coupler support plate 37 and the connecting shaft portions 40,40 are welded to each other, the protrusions of the connecting shaftportions 40, 40 from the welding bores 41, 41 is pushed and crushedaxially and thermally welded to the coupler support plate 37. Therefore,the coupler 37 and the connecting shaft portions 40, 40 can be welded toeach other without need for expensive welding equipment and jig for aultrasonic welding and the like and thus, inexpensive equipment and jigcan be used for the thermal welding. In this case, the weld strength ina direction perpendicular to the axial directions of the welding bores41, 41 can be increased, because the tapered portions 41 a, 41 a withthe diameter increased in the direction away from the end wall 18 a areprovided at ends of the welding bores 41, 41 opposite from the end wall18 a.

Moreover, the connecting shaft portions 40, 40 extend through thethrough-bores 38, 38 provided in the end wall 18 a of the solenoidhousing 18 and hence, the position of the bobbin 23, i.e., the coilassembly relative to the solenoid housing 18 in a plane perpendicular tothe axis of the solenoid housing 18 can be determined constant. Inaddition, the position of the coupler 36 relative to the coil assembly17 in the plane perpendicular to the axis of the solenoid housing 18 canbe determined constant by fitting of the terminal member 35 in thecoupler 36, and the coupler 36 can be fixed firmly and stably to theouter surface of the end wall 18 a of the solenoid housing 18 having arigidity.

The welding bores 41, 41 and the connecting shaft portions 40, 40forming two pairs with each other are disposed at locations where thecoupler 36 is interposed between them and hence, it is possible toreliably achieve the mounting and fixing of the coupler 36 to the outersurface of the end wall 18 a included in the solenoid housing 18. Sincethe coupler support plate 37 is formed into the disk shape, the loadstrength of the coupler 36 in the direction around the entirecircumference of the solenoid housing 18 can be increased.

Additionally, the base portion of the terminal member 35 adjacent thebobbin 23 is covered with a covering portion 42 made of a syntheticresin, formed integrally with the bobbin 23 and fitted in theterminal-penetration bore 39. The guide portion 52 can be utilized forpositioning of the bobbin 23 and the coupler 36 relative to the solenoidhousing 18, while providing the insulation between the terminal member35 and the solenoid housing 18. Thus, in cooperation with the extensionof the connecting shaft portions 40, 40 through the through-bores 38, 38in the solenoid housing 18, the positioning of the bobbin 23 and thecoupler 36 relative to the solenoid housing 18 can be ensured morefirmly.

Further, the collar 27 made of the non-magnetic material for guiding theaxial movement of the movable core 21 is press-fitted in thethrough-bore 26 provided in the central portion of the yoke plate 19 toextend through the through-bore 26, and the outward-facing collarportion 27 a protruding radially outwards and opposed to the innersurface of the center bore 22 in the bobbin 23 is integrally provided atone end of the collar 27. Therefore, it is possible to press-fit thecollar 27 into the through-bore 26 in the yoke plate 19 using theoutward-facing collar portion 27 a exerting no influence to the slidingmovement of the movable core 21 within the collar 27. In this manner, itis possible to achieve the press-fitting of the collar 27 having athickness set at a small value to the utmost. As a result, the distancebetween the movable core 21 and the yoke plate 19 can be set at a smallvalue to the utmost to enhance the magnetic characteristic, and theaxial movement of the movable core 21 can be guided stably by the collar27 fixed to the yoke plate 19.

The cylindrical portion 19 a defining a portion of the through-bore 26is integrally provided in the central portion of the yoke plate 19 toprotrude on the side opposite from the coil assembly 17, and the collar27 is supported over a axially relatively long distance by thecylindrical portion 19 a integral with the yoke plate 19 a. In thismanner, the axis of the collar 27 can be prevented to the utmost frombeing inclined. In addition, the area of a portion of the yoke plate 19opposed to the outer surface of the movable core 21 through the collar27 can be increased, and an enhancement in magnetic characteristic canbe provided by an increase in area of a magnetic path.

In addition, the movable core 21 is integrally provided with thesmaller-diameter portion 21 a inserted into the collar 27, and thelarger-diameter portion 21 b formed with the diameter larger than thatof the smaller-diameter portion 21 a and coaxially connected to one endof the smaller-diameter portion 21 a at the location outside the axiallyone end of the collar in such a manner that it is opposed to the otherend of the stationary core 20. Notwithstanding that the collar 27 isinserted into the center bore 22 in the bobbin, the area of oppositionbetween the movable core 21 and the stationary core 20 is set at arelatively large value, and thus, the magnetic characteristic can befurther enhanced in cooperation with the increase in area of the portionof the yoke plate 19 opposed to the outer surface of the movable core 21through the collar 27.

The recess 29 for accommodation of a portion of the return sprig 28mounted between the movable core 21 and the stationary core 20 iscoaxially provided in one end of the movable core 21 and hence, themovable core 21 can be lightened in weight, despite the provision of thelarger-diameter portion 21 b at one end of the movable core 21, and therapid axial movement of the movable core 21 is possible. The grooves 31defining the flow path 30 between the grooves themselves and the innersurface of the center bore 22 are provided to extend over the axiallyentire length of the larger-diameter portion 21 b and hence, the fluidcan be moved between the opposite ends of the larger-diameter portion 21b with the axial movement of the movable core 21, thereby contributingto the rapid axial movement of the movable core 21. Further, since thecommunication bore 32 is provided in one end of the movable core 21 toconnect the flow path 30 and the recess 29 to each other, the movementof the fluid caused with the movement of the axial movement of themovable core 21 can be smoothened, whereby the movable core 21 can bemoved quickly.

The movable core 21 included in the solenoid section 16 and the rod 50included in the valve section 15 are separated from each other in such amanner that one end of the rod 50 abuts against the other end of themovable core 21. Thus, it is unnecessary to increase the processingaccuracy for the assembling of the movable core 21 and the rod 50, andeven if the axial centers of the movable core 21 and the rod 50 aremisaligned slightly from each other, an adverse influence cannot beexerted to the axial movements of the movable core 21 and the rod 50separately guided by the collar 27 and the guide 52. Therefore, it ispossible to facilitate the processing and assembling of the collar 27,the movable core 21 and the rod 50, thereby providing a reduction incost.

The valve housing 48, the bobbin 23 and the yoke plate 19 are coupledintegrally to one another by molding so that the valve housing 48 in thevalve section 15 is integrally connected to the bobbin 23 through theplurality of connecting bores 54 provided in the yoke plate 19 in thesolenoid section 16. Therefore, it is possible to easily increase theaccuracy of the axial centers of the bobbin 23, the yoke plate 19 andthe valve housing 48.

Moreover, the inward-facing collar portion 27 b protruding the radiallyinwards is integrally provided at the other end of the collar 27, andone end of the rod 50 axially movably passed through the inward-facingcollar portion 27 b is disposed to coaxially abut against the other endof the movable core 21 within the collar 27. Therefore, the other end ofthe collar 27 is substantially occluded by the rod 50 and thus, it ispossible to prevent the entrance of dust into the collar 27 to theutmost.

Further, the abutment face 50 b spherical about the phantom center onthe axis of the rod 50 is formed at one end of the rod 50 to abutagainst the other end of the movable core 21. Therefore, it is possibleto ensure that even if a force from the movable core 21 in a directionoffset from the axis thereof is exerted to the rod 50, an influencecannot be exerted to the axial movement of the rod 50.

The bobbin 23 is provided at one end thereof with the accommodatingrecess 44, which opens in an opposed relation to the end wall 18 a ofthe solenoid housing 18, and the spring 45 made of the conductive metalfor biasing the coil assembly 17 toward the yoke plate 19 is mountedbetween the earth plate 43 accommodated in the accommodating recess 44to lead to the coil 24 and the end wall 18 a. Thus, the earth plate 43can be electrically connected to the solenoid housing 18 using thespring 45 for retaining the coil assembly 17 stably within the solenoidhousing 18, and the solenoid housing 18 can be grounded. In this way, itis unnecessary to mount a grounding terminal member, leading to areduction in number of parts.

To fit and fix the valve seat member 53 of the valve housing 48 in thevalve section 15, the valve seat member 53 having the second valve seat64 at one end is provided at the other end thereof with the limitingcollar portion 53 a protruding the radially outwards, and the valvehousing 48 is provided with the step 65 adapted to abut against thelimiting collar portion 53 a upon the fitting of the valve seat member53 to define the end of movement of the valve seat member 53 in afitting direction. Therefore, in a state in which the valve seat member53 has been fitted and fixed in the valve housing 48, the second valveseat 64 and the step 65 of the valve housing 48 are disposed in axiallydisplaced positions. Thus, the determination of the position of thesecond valve seat 64 corresponding to the diversification of the lengthand the shape of the valve housing 48 can be achieved by only changingthe length between the second valve seat 64 and the limiting collarportion 53 a, leading to enhanced general-purpose properties.

The second valve seat 64 is formed into a tapered shape, which canimprove the seatability of the spherical valve member 49 with respect tothe second valve seat 64 and can maintain a stable seating state of thevalve member 49 when the valve is closed.

To fit the valve seat member 53, the fitting bore 56 is provided in theother end of the valve housing 48 coaxially with the axis of the movablecore 21 to open on the side opposite from the solenoid housing 18 of thesolenoid section 16. The O-ring 66 is mounted on the outer periphery ofthe valve seat member 53 fitted in the fitting bore 56 with the limitingcollar portion 53 a abutting against the annular step 65 formed on theinner surface of the intermediate portion of the fitting bore 56, sothat the O-ring 66 comes into repulsive contact with the inner surfaceof the fitting bore 56. Thus, the valve seat member 53 can be fitted inthe valve housing 48, while maintaining the sealability between thevalve chest 58 and the outside.

Further, the second valve bore 63 is provided in the valve seat member53 over the axially entire length with one end opening into the centralportion of the second valve seat 64; the outer periphery of the filter67, to which the other end faces, is disposed with the limiting collarportion 53 a of the valve seat member 53 interposed between the outerperiphery of the filter 67 and the step 65, and the other end of thevalve housing 48 is engaged with the outer periphery of the filter 67 bycaulking. Therefore, it is possible to facilitate the assembling of thevalve seat member 53 and the filter 67 to the valve housing 48.

The filter 67 comprises the net-shaped member 69 supported on the innerperiphery of the frame member 68 formed into the ring shape, and thesecond valve bore 63 has the tapered bore portion 63 a coaxiallyprovided at the other end thereof, with the diameter of thelarger-diameter end of the tapered bore portion 63 a being larger at alocation closer to the filter 67, while corresponding to the innerdiameter of the frame member 68, so that the fluid flows through thesubstantial entirety of the net-shaped member 69 of the filter 67,whereby the resistance to the flowing of the fluid can be suppressed.

A second embodiment of the present invention will be described be lowwith reference to FIGS. 5 and 6. Spherical valve member guide members 70are integrally connected to one end of a valve seat member 53′ fittedand fixed in a valve housing 48 to come into contact, at a plurality of,e.g., four points around an axis of the valve seat member 53′, with aspherical valve member 49 accommodated in a valve chest 58 to which oneend of the valve seat member 53 faces.

According to the second embodiment, the spherical valve member 49 can beguided with a good accuracy to the first and second valve seats 62 and64, in addition to the effect in the first embodiment.

FIG. 7 shows a modification to the second embodiment. In themodification, the length of the spherical valve member guide portions70′ in a circumferential direction of the valve seat member 53′ may beset at a value larger than that of the spherical valve member guideportions 70 shown in FIG. 6.

Although the embodiments of the present invention have been described indetail, it will be understood that the present invention is not limitedto the above-described embodiments, and various modifications in designmay be made without departing from the spirit and scope of the inventiondefined in the claims.

What is claimed is:
 1. A solenoid valve comprising a coil assemblyincluding a bobbin made of a synthetic resin and having a center bore,and a coil wound around said bobbin, said coil assembly beingaccommodated in a solenoid housing made of a magnetic metal and havingan end wall at one end thereof; a stationary core magnetically coupledto said end wall and inserted into one end of said center bore; amovable core opposed to said stationary core and inserted into the otherend of said center bore; a yoke plate made of a magnetic metal, whichhas a through-bore in its central portion and which is opposed to theother end of said coil assembly and coupled to the other end of saidsolenoid housing; a collar made of a non-magnetic material adapted toguide the axial movement of said movable core and inserted into theother end of said center bore through said through-bore; and a valvemember which is accommodated in a valve housing connected to said yokeplate and to which a rod operatively connected to said movable core isconnected, wherein said valve housing is provided with a guide portionfor guiding the axial movement of said rod, and one end of said rod isput into coaxial abutment against the other end of said movable core. 2.A solenoid valve according to claim 1, wherein said valve housing madeof a synthetic resin is integrally connected to said bobbin through aplurality of connecting bores provided in said yoke plate.
 3. A solenoidvalve according to claim 2, wherein an outer periphery of said yokeplate integrally coupled by molding between said valve housing and saidbobbin is coupled to said solenoid housing on the side opposite fromsaid end wall.
 4. A solenoid valve according to claim 1, wherein saidcollar which has at one end thereof an outward-facing collar portionprotruding radially outwards and opposed to an inner surface of saidcenter bore is press-fitted into said through-bore.
 5. A solenoid valveaccording to claim 4, wherein said collar is provided at the other endthereof with an inward-facing collar portion protruding radiallyoutwards, and one end of said rod through which said inward-facingcollar portion is axially movably passed is put into coaxial abutmentagainst the other end of said movable core within said collar.
 6. Asolenoid valve according to claim 1, wherein said yoke plate has acylindrical portion integrally provided at a center thereof to protrudeon the side opposite from said coil assembly and to define a portion ofsaid through-bore.
 7. A solenoid valve according to claim 1 or 6,wherein said movable core is integrally provided with a smaller-diameterportion inserted into said collar, and a larger-diameter portion formedto have a diameter larger than that of said smaller-diameter portion andcoaxially connected to one end of said smaller-diameter portion at alocation outside axially one end of said collar in such a manner that itis opposed to the other end of said stationary core.
 8. A solenoid valveaccording to claim 7, wherein said movable core has a recess coaxiallyprovided at one end thereof, so that a portion of a return springmounted between said movable and stationary cores is accommodated insaid recess.
 9. A solenoid valve according to claim 7, wherein saidlarger-diameter portion has a groove provided in its outer surface toextend over the axially entire length of the larger-diameter portion todefine a flow path between the outer surface of said larger-diameterportion and the inner surface of said center bore.
 10. A solenoid valveaccording to claim 9, wherein said movable core has a recess coaxiallyprovided at one end thereof, so that a portion of a return springmounted between said movable and stationary cores is accommodated insaid recess, and a communication bore provided at one end thereof toconnect said flow path and said recess to each other.
 11. A solenoidvalve according to claim 1, wherein said rod is formed at one endthereof with an abutment face spherical about a phantom center on theaxis of said rod, said abutment face abutting against the other end ofsaid movable core.
 12. A solenoid valve according to claim 1, whereinsaid bobbin has an accommodating recess provided at one end thereof toopen in an opposed relation to said end wall of said solenoid housing,and a spring made of a conductive metal and adapted to exhibit a springforce for biasing said coil assembly toward said yoke plate is mountedbetween said end wall and an earth plate accommodated in saidaccommodating recess and leading to said coil.
 13. A solenoid valveaccording to claim 1, wherein a connecting shaft portion tightly passedthrough a through-bore provided in said end wall is integrally connectedto said bobbin, and a coupler support plate is integrally formed on acoupler made of a synthetic resin to which a terminal member connectedto said coil faces, so that said coupler support plate abuts against theouter surface of said end wall, said coupler support plate and saidconnecting shaft portion inserted through a welding bore provided insaid coupler support plate being welded to each other.
 14. A solenoidvalve according to claim 13, wherein said coupler support plate isformed integrally with said coupler separate from said coil assembly,and said terminal member passed through a terminal-penetration boreprovided in said end wall is fitted into said coupler.
 15. A solenoidvalve according to claim 13 or 14, wherein at least two sets of saidwelding bores and said connecting shaft portions are disposed atlocations where said coupler is interposed between them.
 16. A solenoidvalve according to claim 13 or 14, wherein said coupler support plate isformed into a disk shape.
 17. A solenoid valve according to claim 13 or14, wherein a protrusion of said connecting shaft portion from saidwelding bore is pushed and crushed axially and thermally welded to saidcoupler support plate.
 18. A solenoid valve according to claim 17,wherein said welding bore is provided, at its end opposite from said endwall, with a tapered portion with its diameter being larger at alocation farther from said end wall.
 19. A solenoid valve according toclaim 13, wherein a base portion of said terminal member adjacent saidbobbin is covered with a covering portion made of a synthetic resinformed integrally with said bobbin and fitted into saidterminal-penetration bore.
 20. A solenoid valve according to claim 1,wherein said valve housing includes a guide bore coaxially communicatingat one end thereof with said through-bore; a partition wall having afirst valve bore through which the other end of said rod coaxiallydisposed in said guide bore is loosely inserted, and a first valve seat,to a central portion of which said first valve bore faces on the sideopposite from said guide bore; and a fitting bore which is disposedcoaxially with said guide bore with the partition wall disposed betweensaid fitting bore and the other end of said guide bore and which has astep facing on the side opposite from said partition wall; and a valveseat member having a second valve seat at one end and provided at theother end with a limiting collar portion protruding radially outwards isfitted and fixed in said fitting bore in such a manner that a valvechest is provided between the valve seat member and the partition walland said limiting collar portion abuts against said step.
 21. A solenoidvalve according to claim 20, wherein said valve seat member has a secondvalve bore provided therein over the axially entire length with one endopening into a central portion of said second valve seat, and a filteris disposed to face the other end of said second valve bore with saidlimiting collar portion of said valve seat member interposed between anouter periphery of said filter and said step, the other end of saidvalve housing being engaged with the outer periphery of said filter bycaulking.
 22. A solenoid valve according to claim 1, wherein a valveseat member is fitted and fixed in said valve housing to define a valvechest between said valve seat member and said valve housing, and saidvalve member is accommodated in said valve chest, so that it can beseated on a valve seat provided on said valve seat member, said valveseat member having said valve seat at one end being provided at theother end thereof with a limiting collar portion protruding radiallyoutwards, said valve housing being provided with a step adapted to abutagainst said limiting collar portion upon fitting of said valve seatmember to define an end of movement of said valve seat member in afitting direction.
 23. A solenoid valve according to claim 22, whereinsaid valve seat is formed into a tapered shape.
 24. A solenoid valveaccording to claim 22, wherein said valve housing is provided with afitting bore coaxial with an axis of said movable core, and an O-ring ismounted to an outer periphery of said valve seat member fitted in saidfitting bore with said limiting collar portion abutting against saidannular step formed on an inner surface of said fitting bore, so thatsaid O-ring comes into repulsive contact with the inner surface of saidfitting bore.
 25. A solenoid valve according to claim 22, wherein valvemember-guide members are integrally connected to one end of said valveseat member to come into contact with said valve member at a pluralityof points around an axis of said valve seat member to guide the movementof said valve member.
 26. A solenoid valve according to claim 22,wherein said valve seat member is formed of a synthetic resin.
 27. Asolenoid valve according to claim 22, wherein said valve seat member isformed of a metal.
 28. A solenoid valve according to claim 24, whereinsaid valve seat member has a valve bore provided therein over theaxially entire length with one end opening into a central portion ofsaid valve seat, and a filter is disposed to face the other end of saidvalve bore with the limiting collar portion of said valve seat memberbeing interposed between an outer periphery of said filter and saidstep, said valve housing being engaged with the outer periphery of saidfilter by caulking.
 29. A solenoid valve according to claim 28, whereinsaid filter comprises a net-shaped member supported on an innerperiphery of a frame member formed into a ring shape, and said valvebore has a tapered bore portion coaxially provided at the other endthereof with the diameter of its larger-diameter end being larger at alocation closer to said filter, while corresponding to the innerdiameter of said frame member.